A connector having a wrong insertion preventive structure of the connector includes a connector described in the following Patent Reference 1. As shown in FIGS. 16 and 17, this connector described in Patent Reference 1 includes a receptacle 110, and an authorized plug 140 connected to the receptacle 110. The opening edge of a shielding case 116 of the receptacle 110 is provided with a wrong insertion preventive guide piece 118, and a recess 148 corresponding to the wrong insertion preventive guide piece 118 is formed in a shielding case 146 of the authorized plug 140. Then, proper connection can be obtained by inserting and fitting the wrong insertion preventive guide piece 118 into the recess 148 in the case of connecting the authorized plug 140 to the receptacle 110.